Field of the Invention:
The invention relates to a device for reducing the frictional force between a guiding or carrying element for sheets in a sheet-processing machine.
It is disclosed in German Published, Non-Prosecuted Patent Application DE 25 05 762 B, corresponding to U.S. Pat. No. 3,951,401 to Marass, to employ for sheets or sheet stacks carrying bars that are used to carry an auxiliary stack, particularly in the case of nonstop feed or delivery. To reduce the frictional force between the carrying bars and the sheet stack, blowing air is blown into the spaces between the carrying bars located at a distance from one another. Seals prevent the blowing air from flowing out and assist the buildup of an appropriate dynamic pressure.
It is accordingly an object of the invention to provide guiding and carrying elements with throttled blowing air that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that reduces frictional force between guiding and carrying elements and sheets of a sheet-processing machine by using blowing air.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for reducing a frictional force between sheets and guiding and carrying devices for sheets in a sheet-processing machine including a sheet transporting element defining a hollow interior, the sheet transporting element having a sheet surface, orifices fluidically connected to the hollow interior, and a throttle disposed in the hollow interior, the sheet transporting element to be connected to an air source for blowing air out through the orifices and for generating an air cushion between a sheet and the sheet surface of the sheet transporting element, and each of the orifices preceded by the throttle with respect to a direction of air from the air source.
One advantage of the invention is that additional sealing measures in the outer region of the sheet stack are no longer necessary.
Throttled nozzles that are disposed directly on the top side and the underside of the carrying bars generate, at the surfaces of contact between carrying bar and sheet, a high dynamic pressure along with a low throughflow. Advantageously, therefore, only a little blowing air escapes from nozzles that are not covered.
In accordance with another feature of the invention, throttled nozzles are used on so-called xe2x80x9cseparating shoesxe2x80x9d that are disposed in the region of the front lay marks on the feed table. The separating shoes are guiding elements that are acted upon by blowing air and are disposed at a distance from one another transversely to the sheet transport direction such that the transporting and aligning device are disposed between the separating shoes. On an underside facing the sheet, the separating shoes have a number of orifices, from which throttled blowing air emerges, and the frictional force between the separating shoes and the sheet is, thus, reduced. Ideally, the sheet is guided, completely free of contact, below the separating shoes. It is advantageously proposed, furthermore, that cover marks be acted upon from inside by throttled blowing air that can emerge from orifices, in particular, on the top side of the cover marks, so that a sheet drawn by the front lay marks comes into contact as little as possible, preferably free of contact, with the cover marks.
In accordance with a further feature of the invention, the throttle is a throttle section.
In accordance with an added feature of the invention, the sheet transporting element is one of a sheet guiding element and a sheet carrying element.
In accordance with an additional feature of the invention, the orifices are throttled air nozzles.
In accordance with yet another feature of the invention, advantageously, the configuration of the throttled nozzles is such that each of the orifices is connected to an air pressure generator through an air throttle. The air throttle may be integrated into the air guidance system at a distance from the respective throttled air nozzle. However, the air throttle and the air nozzle throttled by the air throttle may form a structural unit in the form of a throttle nozzle. In the last-mentioned case, each of the throttled air nozzles is assigned its own air throttle. However, an air throttle may also be provided that is connected pneumatically to a plurality of throttled air nozzles simultaneously through the air guidance system.
In accordance with yet a further feature of the invention, the air throttle has located in it, as its integral part, a so-called packing column, the small packing bodies of which form flow resistances for the suction or blowing air flowing through the air throttle and generated by the air pressure generator.
In accordance with yet an added feature of the invention, the air throttle has located in it, as its integral part, a throttle piece, resembling an air filter, which forms a flow resistance for the suction or blowing air. For example, the throttle piece is a textile layer that may be woven or nonwoven. However, the throttle piece may also be a porous and, therefore, air-permeable sponge that is foamed from a plastic.
In accordance with yet an additional feature of the invention, the air throttle is fitted with air barriers that project into the flow path of the suction or blowing air and that delimit swirl chambers that are disposed between each of the projecting air barriers.
In accordance with again another feature of the invention, the air throttle is configured as a so-called perforated-plate labyrinth. The plates are disposed one above the other and swirl chambers are disposed between each of the perforated plates.
In accordance with again a further feature of the invention, the throttle is a spiral air duct.
In accordance with again an added feature of the invention, the throttled air nozzles are blowing nozzles.
In accordance with again an additional feature of the invention, the orifices are blowing nozzles.
With the objects of the invention in view, there is also provided a device for reducing a frictional force between sheets and an auxiliary stack table for sheets in a feeder of a sheet-processing machine including a rake bar defining a hollow interior. The rake bar has a sheet surface, orifices fluidically connected to the hollow interior, and a throttle disposed in the hollow interior. The rake bar is connected to an air source for blowing air out through the orifices and for generating an air cushion between a sheet and the sheet surface of the rake bar. Each of the orifices is preceded by the throttle with respect to a direction of air from the air source.
With the objects of the invention in view, there is also provided a device for reducing a frictional force between sheets and an auxiliary stack table for sheets in a delivery of a sheet-processing machine including a rake bar defining a hollow interior. The rake bar has a sheet surface, orifices fluidically connected to the hollow interior, and a throttle disposed in the hollow interior. The rake bar is connected to an air source for blowing air out through the orifices and for generating an air cushion between a sheet and the sheet surface of the rake bar. Each of the orifices is preceded by the throttle with respect to a direction of air from the air source.
With the objects of the invention in view, there is also provided a sheet-fed rotary printing machine including sheet guiding and carrying devices and a sheet transporting element for reducing a frictional force between sheets and the guiding and carrying devices. The sheet transporting element cooperates with the sheet guiding and carrying devices to convey sheets in a printing machine. The sheet transporting element defines a hollow interior. The sheet transporting element has a sheet surface, orifices fluidically connected to the hollow interior, and a throttle disposed in the hollow interior. The sheet transporting element is connected to an air source for blowing air out through the orifices and for generating an air cushion between a sheet and the sheet surface of the sheet transporting element. Each of the orifices is preceded by the throttle with respect to a direction of air from the air source.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in guiding and carrying elements with throttled blowing air, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.